Hello all! I understand there is a lot of content in here about ketosis and refeeds but I want to attempt to clarify this idea that refeeds help "boost" your metabolism back up.

McDonald states, "In general, short refeeds, lasting from 5 to 24 hours were used every so often while dieting. Iíve tried them all .... The question is whether or not those programs were optimal. In my opinion, they arenít for several reasons.

One of the factors Iíve been considering to a great degree has to do with the length of the overfeeding period. While itís true that 5 (or 12 or 24) hours of concentrated overfeeding will raise leptin, the more important question is whether thatís sufficient to Ďtellí the brain that youíre fed. While data (especially in humans) is nonexistent, my hunch is no.

Thereís a lag time of several days between the drop in leptin and the drop in metabolic rate (nervous system output) for example; Iíd be surprised if a mere 12 or 24 hours was sufficient to reverse this. Rather, Iíd expect it to take a similar amount of time for the reversal to occur ...

Now, this isnít to say that short carb-loads/refeeds arenít of benefit. They refill glycogen, turn off catabolism and maybe induce an anabolic response to boot. They also let you eat some of the crap youíre really craving which helps psychologically. But I doubt they are sufficient to affect metabolism very much. Instead, a longer refeed is necessary. The drawback, of course, is that longer refeeds have a tendency to put too much bodyfat back on which goes agains the entire goal of dieting."

So can we clarify whether refeeds actually boost the metabolism or not? They have obvious benefits (as he stated), but the main concern is metabolism manipulation. Anyone have any science to back up his claim (or refute it)?

From my understanding of leptin, the small refeeds will NOT boost metabolism. It seems that a minimum of one week of >=150g of carbohydrate consumption is needed to increase leptin, and up to a full 14 days to normalize it completely. And even at this point, leptin will still be slightly downregulated unless you gain all the fat back you lost. Leptin plays a large role in metabolism, so replace everytime I used "leptin" with "metabolism", and you have your answer.

From my understanding of leptin, the small refeeds will NOT boost metabolism. It seems that a minimum of one week of >=150g of carbohydrate consumption is needed to increase leptin, and up to a full 14 days to normalize it completely. And even at this point, leptin will still be slightly downregulated unless you gain all the fat back you lost. Leptin plays a large role in metabolism, so replace everytime I used "leptin" with "metabolism", and you have your answer.

Nope. Leptin will go up in 5 hours of overfeeding. The question is whether or not it can send a useful signal to the brain. The answer is most likely no

From my understanding of leptin, the small refeeds will NOT boost metabolism. It seems that a minimum of one week of >=150g of carbohydrate consumption is needed to increase leptin, and up to a full 14 days to normalize it completely. And even at this point, leptin will still be slightly downregulated unless you gain all the fat back you lost. Leptin plays a large role in metabolism, so replace everytime I used "leptin" with "metabolism", and you have your answer.

Noi no no, your screen name is hysterical because you don't understand squat about physiology

Leptin will go up within 5 hours of high calories/carbs

The issue is whether or not the brain will get enough of a signal to reverse anything

That takes 1-2 days of maintenance calories depending on a host of factors.